The present invention relates to powder compacting apparatus and, more particularly, to an apparatus which produces a compacted article within very close dimensional tolerances in a die cavity between a reciprocable punch and a counterpunch or between a reciprocable punch and an anvil having a portion forming part of a molding cavity.
The present invention is concerned with improved tooling for use in powder-compacting presses such as are disclosed in U.S. Pat. Nos. 3,826,559; 3,775,032; 3,730,659; 3,726,622; 3,645,658; 3,574,892; 3,561,056; 3,415,412; 3,344,213; and 3,328,840, all of which are assigned to the same assignee as the present application.
In the powder-compacting presses disclosed in the aforementioned U.S. patents, articles are compacted and formed in a single or multi-cavity die forming part of a punch and die set, with the finished articles being automatically ejected from the die cavities, picked up by a vacuum pick-up head, and conveyed into suitable receptacles. A work station positioner assembly, which is part of the press, is mounted linearly or angularly movable transversely over the die plate and carries a powder dispenser, an anvil and a pick-up head. The powder dispenser, which is supplied with powder from primary powder supply means connected thereto by means of a flexible tubing or the like, is first positioned over the die cavity which is thus filled with powder as the punch is displaced downwardly so as to draw a predetermined amount of powder into the die cavity. The powder dispenser is then removed from above the die cavity by a subsequent angular or linear motion of the station positioner assembly, and the anvil is, in turn, positioned over the cavity. The anvil is clamped over the die cavity by means of a clamp supported above the anvil and actuated in timed relation with the movement of the punch. The anvil is held down with sufficient pressure to permit compaction of the powder against the anvil as a result of an upward motion of the punch into the die cavity. The anvil is then removed from its position over the die cavity and is replaced by the pick-up head, as a result of a further linear or angular motion of the work station positioner across the face of the die plate. The punch is displaced upwardly so as to bring its upper end in substantial flush alignment with the upper surface of the die plate, such that the finished compacted article is ejected from the die cavity and picked up by the pick-up head for transfer to an appropriate container.
In U.S. Pat. Nos. 3,775,032, 3,826,599, 4,047,864, 4,061,452, 4,061,453 and 4,230,653, also assigned to the same assignee as the present application, tooling arrangements for compacting articles from powder material are described in which a mold cavity is defined partly by the end face of an upper punch projecting through an anvil element above the die cavity, partly by the die bore wall and partly by the end face of the lower punch.
In U.S. application Ser. No. 300,577, filed on Sept. 8, 1981, there is disclosed a molding apparatus in the form of a die having a die cavity, and a punch reciprocably movable in the die cavity for compression powder material filling the die cavity by way of an upwardly directed stroke of the punch. The anvil face against which the powder material is compacted has a movable portion and a stationary portion such that the article is compacted with a portion of its upper face in engagement with the stationary portion of the anvil face and another portion in engagement with the movable portion of the anvil face.
In structures wherein, for example, an upper punch, or counterpunch, is disposed reciprocable in the anvil, or wherein a part of the molding cavity is formed by a portion of the anvil provided with a recess or with a movable section, in order to mold an article with high dimensional and shape accuracy, high precision is required in the making of the punches, counterpunches and anvil, and, in addition, the anvil must be precisely mounted on the work station positioner. The mechanism actuating the work station positioner, either arcuately or linearly, must be machined, assembled, and adjusted within close tolerance limts, in order to precisely align the working face of the anvil, or the counterpunch, with the die cavity. Even though high accuracy in components and assembly may be achieved when the powder compacting apparatus is manufactured, such high accuracy is costly to achieve and gradually deteriorates as a result of normal wear of the parts in motion. Gears develop backlash, and cam and slides are subjected to wear that results in play, lost motion, and gradual decrease in accuracy of the compacted articles, in dimension, in shape and in density. The problem of gradual wear and deterioration is further amplified when the powder material used for compacting articles is substantially abrasive, as is generally the case.